Hello Artec,
All of the comparison pictures I've seen were between the AE 24W and the 24W Boxer but I've heard that the K2000R is nearly identical in performance. In those examples the AE 24W would throw better while the Boxer would probably be considered to have the more utilitarian beam shape since it wasn't as pencil shaped as the AE lights.
The Xenide 25W is noticable brighter than the AE 24W and has a nicer hot spot in my opionion. Although I don't own a K2000R to compare for you, I can offer this. When you have two lights of similar wattage and color temperature they're going to produce close to the same output. When those same two lights have similar sized reflector diameters, the one with the smooth reflector is going to throw about 15%-25% further while the one with the OP reflector is going to offer a much smoother beam.
I used to own the Boxer 24W and currently own the K3500R and think that either of them make better walking lights than a Xenide or AE24/S without a diffuser. A Xenide with a diffuser might just be the best of both worlds though.
Look at the difference in length as the difference between each light's fuel tank size. The Xenide as a big gas tank, the Microfire as a small one. Either battery is proprietary so there is no decided advantage there as there is with the Boxer which takes 168/18650's. You'll just have to decide for yourself if you'd rather have compactness or extended run-time.